The spatial smoothing consists on determining for each point of the land the potential information present in its neighborhood. A Gaussian type statistical function (called BiWeight) is used to weight (w) this information according to the distance from the considered point in kilometers. The formula used is as follows:
w = ( 1 - (d/R)^2)^2
Where w is for weight, d is for distance in Km and R is for smoothing radius in Km.
Gaps in Switzerland and Andorra were covered using auxiliary data. In the case of Switzerland available Level 2 data for 1990 was integrated in the CLC90 layer. In the case of Andorra CLC90 was in fact available due to the overlapping of Spanish and French datasets. Since no data was available for 2000 neither for Switzerland nor for Andorra we assumed that no changes occurred since 1990 in order to produce continuous smoothed layers. However, it should be taken into account that smoothed data for 2000 in these two countries is not real.